Border restrictions can keep COVID-19 cases down, but they don’t necessarily prevent outbreaks from happening, according to a new study from the University of British Columbia.
The research looked at the effectiveness of international travel restrictions at reducing COVID-19 importations and transmission in Canada in the first two waves of 2020 and early 2021.
It was published on eLife on Aug. 2, 2022.
Lead author Angela McLaughlin wrote when Canada closed its borders in March 2020, there was a “drastic reduction” in viral importations.
When Canada introduced restrictions on the entry of foreign nationals on March 21, 2020, there were 10-fold fewer viral importations within four weeks, the study says.
During that first wave in 2020, researchers believe that 49% of COVID-19 importations originated from the United States and were primarily introduced into Quebec (39%) and Ontario (36%).
In the second wave, the U.S. was still a predominant source (43%) for COVID-19, alongside a larger contribution from India (16%) and the U.K. (7%), the study found.
More cases of COVID-19 eventually broke through, and the outbreaks of that summer were soon replaced by coronavirus variants of concern in winter.
Although COVID-19 importations were markedly reduced by travel restrictions, they were not eliminated and continued on at a lower level through the spring and summer of 2020.
This seeded new chains of transmission that subsequently contributed greatly to the persistence of COVID-19 cases in the second wave, the study says.
Importations rebounded further in November 2020, with the easing of entry exceptions for foreign nationals and quarantine shortening, bringing newly emergent variants of concern.
The takeaway of the extensive study, which took two years to complete, is that border restrictions can keep the number of COVID-19 cases down, “with few exemptions, in the absence of rapid testing, which was the case in the first two waves,” as McLaughlin said in a recent interview with CityNews.
“However, they can have a diminishing return if the domestic prevalence in Canada of COVID is quite high,” she said.
The researchers say that travel restrictions and quarantine periods would have needed to be sustained to fully curtail Canada’s COVID-19 burden, but ultimately, those restrictions come with a trade-off.
“The social and economic repercussions of travel restrictions must be weighed relative to the risk of unhampered viral importations, which have the potential to overburden the healthcare system,” said Mclaughlin in a news release.
The study was led by researchers at UBC and the B.C. Centre for Excellence in HIV/AIDS, alongside colleagues from Western University, the University of Arizona, and the Canadian COVID-19 Genomics Network.
The data provides "important insight" into the effectiveness of public health interventions that will help inform how we respond to future viral threats, the researchers say.
“We are now in the era of infectious disease,” said the study’s senior author Dr. Jeffrey B. Joy, an assistant professor at UBC’s department of medicine and senior scientist at BC-CfE. “This study highlights the increasing importance of genomic epidemiology, enabled by sharing of genomic sequence data, in informing and evaluating public health policy to combat current and future viral outbreaks threatening society.”
“Canada has become a total outlier"
As reported in July, mandatory random COVID-19 testing has resumed for travellers entering Canada through four major airports in Vancouver, Calgary, Toronto and Montreal, restoring measures that were paused in June.
Now, randomized testing for all air travellers – fully vaccinated and partially or unvaccinated – is completed outside of airports, either via an in-person appointment at select provider locations and pharmacies, or via virtual appointment for a swab test.
Travellers who do not qualify as fully vaccinated, unless exempt, must continue to test on day one and day eight of their mandatory 14-day quarantine
In response to the program’s return, the Canadian Travel and Tourism Roundtable, a coalition of industry leaders, said it was “a step backward that unfairly targets Canada's tourism sector and negatively impacts Canadian and international travellers.”
“Medical experts have been clear – mandatory testing should be replaced by more effective ways to assess community spread, such as community wastewater testing for tracking future variants,” the Roundtable said in a statement on July 14.
The International Air Transport Association (IATA) has slammed Canada’s decision to keep travel restrictions as other countries around the world lift theirs.
In a statement last month, IATA said the Canadian government’s restrictions are “partly responsible for the ongoing delays and disruption affecting air travellers across Canada.”
“Canada has become a total outlier in managing COVID-19 and travel,” stated Peter Cerda, IATA’s regional vice-president for the Americas. “While governments across the globe are rolling back restrictions, the Government of Canada is reinstating them.”
The Canadian government maintains that data from its on-arrival testing program is used to understand the current level and trends of importation of COVID-19 into Canada.